Index >> Population Interactions >> Classification of Population Interaction

Synergism
Synergism or proto-cooperation between two populations indicates that both populations benefit from the relationship but that the association is not obligatory. Both populations are capable of surviving independently, although they both gain advantage from the synergistic relationship. Such interactions are loose in that one member can be readily replaced by another. One form of synergism, syntrophism, occurs as a result of cross-feeding, in which the two populations supply each other's nutritional needs.

Mutualism
Otherwise known as symbiosis, mutualism is an obligatory interrelationship between two populations that benefits both of them. Mutualism is an extension of synergism, allowing populations to unite arid establish essentially a single unit population that can occupy habitats unfavourable for the existence of either population alone. Mutualistic interactions may lead to the evolution of new organisms. It occurs when two populations are striving for the same resource. It usually focuses on a nutrient present in limited concentrations although it may also occur for other resources including light and space. As a result of this both populations achieve lower densities than would have been achieved by the individual populations in the absence of competition. Competitive interactions tend to bring about ecological separation of closely related populations, a fact known as the competitive exclusion principle. Competition prevents two populations from occupying the same ecological niche for the same nutrient resources.

Parasitism
In this kind of relationship, the parasite population is benefited and the host population is harmed. Parasitic relationships are characterised by a relatively long period of contact, and the parasite is smaller than the host. The host­-parasite relationship is typically quite specific. Such host-parasite relationships that cause disease syndromes clearly exert a negative influence on the susceptible host and benefit the parasite.

Predation
It is another kind of relationship similar to parasitism but differing from it in the fact that here the predator is larger than the prey and that this kind of relationship is a short-term one and is not quite specific.